1. Field of the Invention
The field of the invention is Radio Frequency Identification (RFID) and details an RFID precisely tuned antenna manufacturing method whereby the RFID antenna becomes an integral part of a nano sized integrated circuit package. The RFID manufacturing system contemplated by this invention includes photoresist manufacturing techniques to produce a template or die specifically designed to mass produce RFID transponders whereby the chip and antenna becomes one integrated unit. The RFID antenna template or die is precisely tuned, using trimming algorithms and laser technology, to resonate with electro magnetic signal increments of 2 megahertz. This invention reduces signal to noise ratio by producing precisely tuned antennas which provide a gatekeeper function directly correlated to ambient electro magnetic signals.
2. Description of Related Art
The current state of the art in RFID chip manufacture is represented by Hitachi. RFID chips manufactured by Hitachi are 0.002 inches by 0.002 inches, in other words, the thickness of a piece of paper. These chips resemble a tiny bit of powder yet they can handle the same amount of data as a chip sixty times that size. The data is stored as a 38 digit number. These chips do not contain an external antenna. If this chip did have an external antenna by using current manufacturing methods the external antenna would be much larger than the chips whose signals it would broadcast. For example the chips which use attached antenna use the smallest antenna in the current RFID arsenal which is about 0.16 inches, far larger than the chip itself. The Hitachi chip has yet to find an antenna to compliment its size. In other words, it is a chip without an antenna from which to receive or broadcast its data.
A study by Leisten et. al. titled “Laser Assisted Manufacture for Performance Optimised, Dielectrically Loaded GPS Antennas for Mobil Telephones” sponsored in part by Loughborough University indicates that laser technology is critical to producing precise antenna components. This study underscores the fact that novel laser imaging technology using a positive electrophoretic photoresist and UV eximer laser mask has been developed to produce precise conducting features on the surface of an antenna. During the research a laser trimming technique is tested using trimming algorithms to machine the antennas to operate at precisely 1572.42 MHz, the designated test frequency. The goal was to trim the antenna to within a tolerance of 2 MHz. The trimming was required despite the excellent accuracy which can be achieved with laser imaging of the original antenna pattern. Trimming is necessary as a consequence of the spread in antenna dimensions, dielectric properties to the ceramic core material of the antenna plus copper thickness and resistivity. The antenna trimming was carried out with a fundamental mode Nd:YAG laser in TEM00 mode, resulting in a small laser spot size. The laser beam is focused onto the antenna by means of a flat field (f-theta) lens, and scanned across the top surface of the antenna by means of an x-y galvanometer in order to ablate small areas of copper.
The laser trimming tool is integrated in a robotic assembly loop which fits the matching boxes to the antennas. A pick and place robot picks up an antenna with fitted matching box and places this in a pneumatically actuated chuck on a high speed linear stage which moves the antenna into the laser safe trimming tool enclosure through a pneumatically operated door. Once in the trimming position, four RF probes mounted radially around the antenna are moved to close proximity of the antenna perimeter such that each probe is located at the base of the antenna. The resonant frequency and balance (impedance) of the antenna is measured with the probes and a network analyzer, with specially developed trimming algorithms, determines the amount of copper (if any) needed to be removed from each of the antenna pattern. After the trimming operation, the antenna was again measured with the RF probes and either accepted or rejected pursuant to the tolerance limits of 2 MHz. All accepted antennas are marked with a unique data code that is produced with the same trimming laser. The research concluded that laser technology can fulfill a critical role in the high volume manufacture of small antennas. The research does not contemplate the use of lasers to fine tune an ultra small antenna for transmissions within very narrow ranges to resonant with individual items located in a supply chain or within a warehouse, distribution center or retail environment.
In a study by Penn et al. titled “Development of a 24- to 44-Gigahertz (Ka-band) Vector Modulator Monolithic Microwave Integrated Circuit (MMIC)” the authors conducted research into development of a transponder capable of supporting high data rates of hundreds of Mb/s. Applications considered by the research were Mars missions, lunar missions, astronaut video and high definition television. The research parameters included the need to simplify the transponder hardware by modulating directly at Ka-band. The researchers developed a low power high modulation bandwidth vector modulator under the Mars Advanced Technology Program for Ka-band operation. Their design is capable of space applications from 24 to 44 GHz. It was developed for a transponder operating at the 32 GHz level. This research demonstrates the viability of transponders in the 24 to 44 GHz range but does not contemplate the use of same for ultra small antenna transmission in a supply chain or warehouse, distribution center or retail type of environment.
Fractus, a pioneer developer of the fractal antenna technology, has set a new benchmark for miniaturization. Its smallest antenna is designed for the ISM 2.4 GHz band. The 3.7 mm by 2 mm Micro Reach Xtend antenna is the size of a single grain of rice. This provides device designers with significantly more available space to enable new multimedia applications for such things as Bluetooth headsets and mobile handsets. This use of fractal geometry for an extremely economical use of space is presented by Fractus at a reduced cost; however, it does nothing in terms of providing an on chip antenna for the new dust sized chips. It is simply too big. U.S. Pat. No. 7,095,372 assigned to Fractus, S. A. relates to an integrated circuit package which comprises a substrate which includes an antenna. In the Fractus system miniaturization is accomplished through implanting a series of five segments with at least three of the segments being shorter than one-tenth of the longest free space operating wavelength of the antenna. Furthermore each of the four pairs of angles between sections is to have angles of less than 180 degrees. The Fractus invention allows for a high package density, including the antenna, within the chip. The antenna comprises a conducting pattern at least a portion of which includes a curve of at least five segments. This invention does not contemplate etching a precisely tuned antenna unto silicon as a process of miniaturization.
The present invention piggy backs on the current trend in the semiconductor industry towards System on Chip (SoC) and System on Package (SoP) concepts. These concepts refer to putting all items necessary for chip operation within the chip itself. This invention relates to the RFID industry in particular and its requirements for a miniature antenna to form an integral part of the transponder item found in a complete RFID system. Through integration of the antenna, processors, memories, logic gates and biasing circuitry into a single semiconductor chip, the manufacturing process outlined herein details commercial transponder advantages of size, weight and cost. In other words, by manufacturing the antenna as part of the chip and not by attaching an external antenna, the cost decreases as does the size and weight of the RFID transponder. Furthermore, the present invention borrows from Gen 2 cellular telephony designs by incorporating a frequency division concept into this novel RFID transponder formula.